hot water stopped heating overnight

Thanks for the helpful pictures. They show what looks to my inexpert eye to be a completely normal Economy 7 arrangement, so nothing unorthodox about it that I can see.

In the Consumer Unit, we see the offpeak stuff (i.e. wired to the switched circuit) at the left hand end, with breakers for 1. Storage htr., 2. Water htr., and 3. unknown, but at only 6A, probably not another storage heater. Further to the right, beyond the main switch we see another breaker labelled I.H., which I guess to mean Immersion Heater.  

If that is the case, then the switch we can’t see in your airing cupboard (?) beside the one marked offpeak is the ‘boost’ switch I mentioned earlier. Can you see the end of another element like the one in your penultimate picture, just higher up?
  

If so, it seems likely that the lower (offpeak) element has failed - assuming someone has checked the fuse in that ‘offpeak’ switch. That will need an electrician to sort out, but meanwhile, does the other switch help? Remember that if it does indeed control a secondary (higher up) heating element, it will run at peak price during the day, and it will only heat the top ¼ - ⅓ of the tank. 

I can’t see any way that the meter could be responsible for delivering power to the storage heaters but not to the offpeak water heater. They’re all supplied by the same feed, labelled L5.

Thank you all very much. I’m having it looked at again on Friday with all of your info in mind. If it’s fixed, I’ll cancel the smart meter health check, will keep you posted :-)

Is it just me or does it look like a crack by the fuse holder for the circuit switch with the neon indicator?

You mean this?
 

  
Yep, looks like it. Perhaps caused by a bit of heavy-handed screwdriving to extract the fuse. It doesn’t look particularly dangerous, and I wouldn’t expect it to cause an interruption to the supply to the immersion heater. Stuey might want to have a look at it just to make sure the fuse is intact and in good shape.

​@Firedog ​@BPLightlog thanks for your great advice here, and ​@Gilan02 thanks to you too - good to hear from you.

​@Stuey2026 let us know how it goes - it’ll be great if this can be sorted along with the advice you’ve been given by the community.

Hey ​@Stuey2026 

Thanks for coming back to the thread with that update, I’m glad to hear you’ve got that sorted now.

Do feel free to pop back any time if you’ve ever got any other questions or queries.😊